This invention relates to apparatus for controlling the operation of a currency changer and, in particular, to apparatus for controlling the operation of a currency changer including a paper currency acceptor.
Devices that perform one or more tests on U.S. one-dollar bills or other paper currency to determine their genuineness as a preliminary, for example, to dispensing change are well known in the art. Typically in such devices, the paper currency being validated is moved over a path along which various optical, magnetic or edge-sensing tests are performed. On failing any of these tests, the bill is moved along the path in a reverse direction to be returned to the user, and no credit is given. For example, in the apparatus disclosed in my prior patent, U.S. Pat. No. 3,966,047, a bill is moved along a path at a uniform rate of speed past a pair of photocells spaced farther apart then the length of the bill. If both photocells are covered simultaneously, the inserted object is rejected, since it cannot be a genuine bill.
Paper currency acceptors such as described in my prior patent, being sensitive only to simultaneous patterns of actuation of two or more edge sensors, in effect discard potentially valuable information indicative of attempts to defraud. For example, if a user attempts to cheat the currency acceptor by attaching a pull-back tape to the trailing edge of the bill, tension on the tape will tend to slow the transport motor or cause slippage, increasing the period during which a given sensor is actuated as well as the delay between the actuation of two successive sensors. An acceptor of the type described, however, will only sense the tape if it happens to actuate one of the sensors, as it is insensitive to changes in speed. While such acceptors typically subject the bill to one or more additional tests, their failure to detect an initial attempt to cheat increases the chance that such an attempt will be successful.
Paper currency acceptors of the prior art also present problems of adjustment to accept a reasonable range of acceptable bills which may be dirty or tattered to a greater or lesser degree. Since, typically, the events precipitating rejection follow in relatively close succession, it is difficult to identify the particular malfunction which results in rejection of a genuine bill within the range or acceptance of a spurious bill without individually testing a multiplicity of points in the electronic circuit. Such a trial-and-error approach obviously increases the labor costs of repair, particularly where the bill is subjected to a large number of tests.
Finally, with paper currency acceptors of the prior art, there is always the chance that an inserted bill, particularly if it is worn or has torn edges, will become jammed in the transport. The acceptor must then remain out of service until a serviceman is available.
Paper currency acceptors are often incorporated into bill and coin changers, the coin-accepting and coin-dispensing portions of which present problems similar or analogous to those discussed above. Thus, a mechanical or electrical component failure can often be identified only by a trial-and-error technique of testing individual points in the circuit, again resulting in high labor costs.
Further, unless proper action is quickly taken, certain failures can result in injury to other components, as burning out a solenoid or other electromechanical component. Component failures or erroneous sequences of operation in the coin-dispensing portion of a bill and coin changer can also be costly if they result in "jackpotting", or the uncontrolled dispensing of change. Even in the absence of solenoid burnout or jackpotting, improper operation of a bill and coin changer is highly undesirable if money inserted by a user is accepted without proper change being given.